The present invention relates generally to a point-to-point soldering apparatus and method. More particularly, the invention relates to an automated point-to-point soldering apparatus and method wherein a heat source, or soldering tool, and a solder material source are moveable and positionable independently with respect to one another.
A great number of electronic manufacturing and packaging applications require precise soldering at particular locations on a workpiece, such as for mounting and connecting component leads on a printed circuit board. While many soldering operations may be made at once in devices such as wave soldering machines, other applications require soldering of components on the "top side" of a workpiece, effectively precluding wave soldering. A technique that has been developed for such applications is point-to-point soldering, in which a heat source, such as a hot iron soldering tool, melts solder wire at the solder point to cause the desired quantity of material to flow around the solder point.
Known point-to-point soldering devices are automated to increase production rate and accuracy, often incorporating a programmable controller for storing and executing a preset routine for a particular workpiece configuration. These conventional point-to-point soldering devices include a robot on which a soldering tool and a solder material feed tip are mounted. The robot moves the soldering tool and feed tip into position at or near the solder points, where the controller causes the tool and feed tip to deposit a predetermined quantity of solder material. Moreover, because the soldering tool and feed tip are mounted in a single robot positioner in these soldering devices, the trajectories of the tool and feed tip between solder points are not independent of one another, and thus may not be independently optimized. Furthermore, during soldering operations at each solder point, the orientation of the soldering tool with respect to the feed tip is generally fixed. As a result, such devices cannot effectively reach solder points deep between surface mounted components, limiting the level of integration of circuits and requiring expensive and time-consuming hand soldering of such difficult to reach points.
A further drawback of known point-to-point soldering devices is the lack of mobility of the soldering tool and solder material feed tip during a soldering operation at a particular solder point. In many soldering operations, particularly on larger terminal attachments, less than optimal flow of solder material can result in so-called cold soldering effects, that is, inferior solder joints due to crystallization of solder material during flow at the solder point. While such effects can be avoided by displacing the material feed tip or the soldering tool, or both, during the soldering operation, conventional point-to-point soldering apparatus are generally incapable of such movement because the material feed tip is mounted on the same positioner as the soldering tool.
In addition, while known point-to-point soldering devices are automated and programmable, they are generally programmed to execute a preset routine on a single workpiece configuration. Thus, if workpieces of different configurations are to be soldered, the program must be changed or a different program must be selected from among various preset routines by operator intervention. Such intervention is both time consuming and seriously limits the flexibility of the device in processing small quantities of different workpieces.
Finally, where hot metal soldering tools are used as a heat source, as in many industrial applications, tool tip wear occurs due to heating, contact with solder points and repeated cleaning of the tool. When tools become excessively worn, the quality of contact with solder points is reduced, resulting in less than optimal soldering. In known point-to-point soldering devices, such tool wear is generally either estimated and tools changed on a periodic basis, or measured by operator intervention. In the former case tools may not be used to their full potential, while in this latter case soldering must be halted for the time required for operator intervention, resulting in expensive down-time.
The present invention advantageously provides an apparatus and method for point-to-point soldering that permit independent positioning of a heat source and a solder material source so their angular orientation with respect to one another may be independently controlled to successfully solder difficult to reach solder points.
The present invention also provides an apparatus and method for point-to-point soldering permitting independent optimization of the trajectories of a heat source and a solder material source between solder points.
Moreover, the present invention provides an apparatus and method for point-to-point soldering wherein independent displacement of a soldering tool and a solder material feed device is possible during a soldering operation to avoid cold soldering effects.
The present invention further provides an apparatus and method for programmable point-to-point soldering capable of executing a variety of preset soldering routines on workpieces of different configuration without the need for operator intervention.
The present invention also advantageously provides an automated point-to-point soldering apparatus capable of detecting soldering tool wear and replacing worn tools automatically.